The purpose of the proposed research will be to elucidate the mechanism of action of female sex hormones on tissues of the oral cavity. Phase 1 of the project will determine the optimum conditions under which the presence of hormone "receptors" in non-target tissues could be detected. The search for these "receptors" will be conducted in Phase 2. In addition, Phase 1 will explore the role played by histamine in the oral tissue's response to female sex hormones. Phase 3 will test the human female gingival tissues for "receptor" proteins, and correlate these findings with clinical and histological observations.